ADS8688 with Arduino DUE

Hi,

I am using ADS8688 with my arduino due, if i set channels 0-3 to gnd i get
this as answear, but i expect something about  32768.

CH0: 64
CH1: 64000
CH2: 0
CH3: 256
 
CH0: 192
CH1: 63904
CH2: 32
CH3: 64
 
CH0: 0
CH1: 63520
CH2: 752
CH3: 63552

my setup an code is.

RST/PD -> 3V3

REFSEL -> GND

AVVD -> 5V

DVDD -> 3V3

daisy - > GND

REFGND - > GND

my code is:

#include "SPI.h"    

#define CS         49

int result0;  
int result1;
int result2;
int result3;

void setup() {

pinMode(CS, OUTPUT);          // Chip Select als Output
digitalWrite(CS, HIGH);       // CS High
SPI.begin();                  // SPI start
SPI.setDataMode(SPI_MODE1);   // SPI Mode 1
SPI.setBitOrder(MSBFIRST);  
Serial.begin(9600);           

digitalWrite(CS,LOW);
SPI.transfer16(0x8500);     // device Reset
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0xA000);    // Auto Channel with Reset
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x010F);     // channel 0-3 enable
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x02F0);     //Channel 4-7 Power Down
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0300);     // SDO Output format MSB first
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0501);  // Vref Channel0 +- 1.25 * 4.096
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0601);  // Vref Channel1 +- 1.25 * 4.096
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0701);  // Vref Channel2 +- 1.25 * 4.096
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0801);  // Vref Channel3 +- 1.25 * 4.096  
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0xA000);              // start sampling
digitalWrite(CS,HIGH);
}

void loop() {

digitalWrite(CS,LOW);
SPI.transfer16(0x0000);              // start sampling
result0 = SPI.transfer16(0x0000);    // Channel 0 Data
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0000);              // start sampling  
result1 = SPI.transfer16(0x0000);    // Channel 1 Data
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0000);              // start sampling  
result2 = SPI.transfer16(0x0000);    // Channel 2 Data
digitalWrite(CS,HIGH);
digitalWrite(CS,LOW);
SPI.transfer16(0x0000);              // start sampling  
result3 = SPI.transfer16(0x0000);    // Channel 3 Data
digitalWrite(CS,HIGH);


Serial.print("CH0: ");
Serial.println(result0);
Serial.print("CH1: ");
Serial.println(result1);
Serial.print("CH2: ");
Serial.println(result2);
Serial.print("CH3: ");
Serial.println(result3);
Serial.println(" ");

delay(1000);

}

I do not know whether the device is defect or my code is wrong

Thanks